The present invention relates generally to a method and a device for detecting engine idling. More particularly, the invention relates to a method and device for detecting engine idling based on both the throttle valve angular position and the intake air flow rate.
Generally, engine idling is detected by a throttle switch which is closed when the throttle valve is fully closed and/or the throttle valve open angle is less than a threshold value. Such a throttle switch requires relatively high accuracy for detection of the throttle angular position to produce a signal in response to the shifting of the throttle valve into the engine idle condition. Particularly, for an engine having a relatively large diameter induction system, such as, for example, the induction passage having a single barrel type throttle chamber, variation of air flow rate in response to varying of the throttle valve angular position is remarkable to make the detection of idling condition difficult. Therefore, for such engine, it is important to provide an accurate throttle switch.
On the other hand, the engine idling condition may be detected by detecting the air flow rate lower than a threshold value defining the idle air flow rate. If the engine idling condition is detected based on the air flow rate, the throttle switch will not be required to have as high an accuracy as that otherwise required.